With the use of any form of electrical appliance, there is a need to electrically insulate conductors. With the push to continuously reduce the size and to streamline all electrical and electronic systems, there is a corresponding need to find better and more compact insulators and insulation systems.
Good electrical insulators, by their very nature, also tend to be good thermal insulators, which is undesirable. Thermal insulating behavior, particularly for air-cooled electrical equipment and components, reduces the efficiency and durability of the components as well as the equipment as a whole. It is desirable to produce electrical insulation systems which have maximum electrical insulation and minimal thermal insulation characteristics.
Electrical insulation often appears in the form of tapes, which themselves have various layers. Common to these types of tapes is a paper layer that is bonded at an interface to a fiber layer, both layers tending to be impregnated with a resin. A favored type of insulation material is a mica-tape. Improvements to mica tapes include catalyzed mica tapes as taught in U.S. Pat. No. 6,103,882. The mica-tape may be wound around conductors to provide extremely good electrical insulation. An example of this is shown in FIG. 1. Illustrated here is a coil 13, comprising a plurality of turns of conductors 14, which in the example illustrated here are bakelized coils. The turn insulation 15 is prepared from a fibrous sheet or strip which may be impregnated with a resin. Ground insulation for the coil is provided by wrapping one or more layers of composite mica tape 16 about the turn 14. Such composite tape may be a paper, or a felt of laid down small mica flakes. The composite may also comprise a pliable backing sheet 18 of, for example, glass fiber cloth or polyethylene glycol terephthalate mat, having a layer of mica, usually in the form of flakes 20, bonded thereto by a liquid resinous binder. Generally, a plurality of layers of the composite tape 16 are wrapped about the coil depending upon voltage requirements. To impart better abrasion resistance and to secure a tighter insulation, a wrapping of an outer tape 21 of a tough fibrous material, for example, glass fiber, or the like is applied to the coil.
Generally, multiple layers of the mica tape 16 are wrapped about the coil with sixteen or more layers generally used for high voltage coils. Unfortunately, this amount of insulation only further adds to the complications of dissipating heat. What is needed is electrical insulation that can conduct heat higher than that of conventional methods, but that does not compromise the electrical insulation and other performance factors. Other problems with the prior art also exist, some of which will be apparent upon further reading.